The present invention relates to a cleaning agent and a cleaning process for cleaning poorly accessible machine parts, such as in the transport and/or molding of materials in a pasty state, in particular in combination with the changeover of the processed material. This principally involves the removal of molding material residues on changeover to another material. Thus, this invention relates to a simplification of the changeover of molding material to be processed in plastic-processing machines, such as extruders, injection-molding machines, and blow-molding equipment by accelerating the removal of a previous substance from the plasticizer unit and the nozzle region; an analogous field of use of this invention is, for example, in the operation of kneaders.
A wide variety of different cleaning agents have been used in technical and household applications. For example, French Reference A-2,593,187 relates to a degreasing agent for metal and plastics parts, the degreasing agent containing, apart from water and sodium metasiliate, glycol ethers and alkylbenzene sulfonates as active ingrediants.
U.S. Pat. No. 3,367,878 discloses a cleaning agent for removing asphalt, sodium and/or metallic soap greases, road dirt, forming and cutting oils, and aviation dirt from ferrous and non-ferrous metal surfaces. The cleaning agent contains specific glycols, such as hexylene glycol and propylene glycol, as active ingredients together with a specific organic chelating ingredient, namely the tetrasodium salt of ethylene diamine tetraacetic acid in combination with water and sodium salts.
A cleanser for removing lard and other grease at temperatures of about 65.6.degree. C. from ovens, cookers, pots and tiles is described in German Reference 2,300,744. This cleanser is a water-comprising composition with ammonia, or an organic amine together with organic cleaning compounds, and specific organic amides. The inorganic material which is also present in the cleanser German Reference 2,300,744 is, at least partly, an abrading agent.
In the production of defined moldings from pasty materials, such as thermoplastics or duroplastics, and also in the processing of other substances in the softened state, as the melt or paste, the following has been experienced: in machine parts which come into contact with the viscous molding material, for example the plasticizer unit and the nozzle in injection molding, moulding material is retained. These residues are gradually discharged on changeover and contaminate the subsequent moldings and result in moldings which are unusable for aesthetic or physical reasons.
This problem occurs, for example, in the plastics-processing industry when the color is changed within a series. There are considerable losses in time, energy and raw materials until products of perfect color are achieved.
Thus, it can be expected that a throughput of 650 kg of ABS (acrylonitrile-butadiene-styrene) material will be needed until pure white moldings are produced in a customary injection-molding manufacture of parts weighing 350 g on changing color from a beige ABS material to a similar white material.
The cleaning process outlined above, i.e. working with new material until perfect moldings are achieved, and discarding the unusable moldings made of a mixed material, cannot be justified from economics, such as material and energy costs for unusable products, and disposal, such as burden on dumps caused by unusable and substantially undecomposable moldings, environmental pollution on incineration, and poor opportunity for recycling due to the material mixture.
Disassembly and manual cleaning is likewise an expensive method. In order to circumvent this problem, a further method is known from the prior art.
This involves the introduction of abrasion particles, for example Al.sub.2 O.sub.3, in suspension with organic solvents. The abrasion particles are added to the feed hopper of the plasticator together with the solvent, usually an aromatic, and the starting material in granule, chip or other form. Due to the combined action of the organic solvent, which at least causes the material residues in the screw channel and in the nozzles to swell, thus simplifying removal, and the abrasive action of the abrasion particles, the amount of unusable moldings made from a mixed material is significantly reduced due to the more rapid removal of residual substances.
However, cleaning agents of this type are not without problems from industrial safety and environmental standpoints.
The transport, storage and handling of cleaning agents of this type are associated with risks due to the necessary presence of organic solvents, whose flammability and/or toxicity makes them potential hazards.
For labor and property protection reasons, their handling is subject to official regulations, for example: West German Flammable Liquids Regulations; Transport of Hazardous Materials Regulations; Chemicals Act; Hazardous Industrial Materials Regulations. Since it is necessary for vapors to escape when these substances are warmed in the machine, the guide concentrations (MAC values) can easily be exceeded locally.
In addition, the amounts used are not inconsiderable. Depending on the dimensions of the machine to be cleaned, 0.2 1 to 1.5 1 of suspension are employed per changeover. The stocks in the plant must be arranged appropriately, which means that there is a considerable long-term risk.
In addition, the low stability of the suspensions results in careful mixing being necessary before use if the desired degree of distribution in the starting material, and thus the desired action, are to be achieved.